Question
I'm looking for a nice specimen tree for a small residential yard in San Diego.  Needs to provide shade (a canopy shape would be great) and not make a mess.  Will get full sun, but shade in late afternoon.  Any suggestions?

Answer
There is too many variables to give a good answer. There are many trees that will fit but it will depend on how large of a tree you want, flowering tree, tree for color, space it will be planted in, etc.. I would suggest you visit a local nursery and give them answers about your yard and ask them for advice. You can also look at the different trees there and see one that you like.